Synchronizing system



April 3, 1945. F. R, BRlCK l n 2,37?,762

sYNCHRoNIzING SYSTEM Filed Feb. 20, 1943 2 Sheets-Sheet 1 AMPLI/'75? April 3, 1945. F., R. BRICK f SYNCHRONIZING' SYSTEM 2 Sheets-Sheet 2 Filed Feb. 20, 1945 l AMPLI/'75K INVENTOR. BY M @fw which-necessarily had to be stopped.

i patented malais .UNITED STATES PATENT OFFICE sYNoHRoNrzmG SYSTEM Frank B.. Brick, Elizabeth, N. J. Appiieatmnrebmary 20.1943, serial'No. 476,561 17 claims. (ci. 17a-69.5)

A.My invention relates in general to the iield of facsimile transmission 4and reception and more f particularly concerns a novel method for maintaining facsimile apparatus at remotely disposed stations in synchronism.

In facsimile systems, a scanning member at the ftransmitter traverses an image and generates eletrical currents iiuctuating in accordance with the lights and shades of elementalreas thereof. vThese currents are then transmitted by wire or radiation to a distant receiver where these currents are amplified and applied to a scanning member operable under the surface of a recording sheet.

It is essential that the scanning members at the transmitter and the receiver Abe operated at idenand recorders'vhich may be operated from the same alternating current power line may beI operated in synchronism with each other without the use of special synchronizing equipment. This, of course, may be accomplished by employing similar synchronous drivingimotors at both the transmitter and recorder which, when energized'by valternating current power transmission system.`

In fact, in mobile equipment such as facsimile de. vices adapted for aerial installations, the power supplies are usually of the direct current type and thus there is no common power supply which may tical speeds and corresponding phase positions.k

Heretofore, a start stop synchronizing method was employed in which the transmittingv scanner was operated at a substantially predetermined speed V while the receiving scanner was operated at a somewhat higher speed.

Periodically,- at the termination of each scanning cycle apparatus would be halted and would then be released upon the receipt of a'synchronir- 4 ing signal generated at the transmitter.

The transmitter synchronizing signal normally would be a pulse of relatively short duration which whenV received, would energize solenoidal means to release the scanning halting mechanism. The disadvantages of the' start-stop synchronizing system are wellknown in the facsimile art.' It is recognized that this system has been the prime cause of wear in facsimile equipment.

' 'I'his wear would be the result of the periodic haltins and thus jarring of the relatively large masses The start-stop system was also a severe limitation to high speed facsimile operation. Thus a receiver whenoperated in a start-stop manner,

at relatively high speeds, would soon develop mechanical faults which required constant servic- `ing. lFurthermore, the start-stop system de- In order'to eliminate the deleterious effects ofv continuous stopping and starting of the recording,

equipment, I propose to utilize a continuous synchronizing systemwherein both transmitter and recorder scanning members operatecontinuously synchrcnism with respect toeach be reliedA upon to effect a coordination of the movements of the transmitter and receiverscanning members- More specifically, my invention contemplates the operation of a facsimile recorder from a direct current power supply at a, synchronous speed which is determined by the speed of the facsimile transmitting scanner. I may operate my facsimile transmitting scanner from any available power supply. Should the power supply be of the alternating current type, then I utilize a synchronous motor at the transmitter to drive the scanning members at a corresponding speed. The picture currents generated by the scanning member are applied to an amplifier and are then caused to modulate a radio frequency carrier for transmission purposes.. In addition to the picture current modulation, I may continuously modulate the radio frequency carrier with a synchronizing current which is a function of the -frequencyof the current driving the transmitting synchronous motor. synchronizing current is continuous and may. comprise a modulation at the power system frequency.

The picture currents may themselves bea modulated audio frequency carrier in-order to preclude interference between, the Arelatively low frel quency synchronizing current and the picture at identically the same speed and in the same phase throughout the recording process.

Itwill be evident that facsimile transmitters vamsmis'driven currents. The transmitted wave which therefore comprises a radio frequency Vtangier modulated by a picturecurrent of audio frequency and by a f synchronizing current of power frequency is then L intercepted and detected at 'the receiver. Y

Here the picture and synchronizing currentsv` are separated and selectively applied ing mechanism 'and to a. synchronizing mecha.- nismrespectivly. Therecordinscanningmechf from a local source of elecirical'energy which may Y tarecordby asynchronous motor energized lbein the form of a direct current battery or power In order to translate the electrical energy of the direct current supply to alternating currents of synchronous frequency, I utilize a thyratron inverting circuit which operates to convert energy delivered by the battery into an alternating current suitable for driving the scanning means. The frequency of the alternating current delivered by a thyratron inverter is exactly that of an impressed synchronizing frequency which in this example is the transmitted power frequency synchronizing current.

Thus it will be evident thatthe synchronous receiving motor drives the recording mechanism atsynchronous speed vwhile deriving its energy from a direct current power supply. Accordingly the need for a start-stop mechanism has been eliminated entirely.

In another modification of my continuous synchronizing system. I may employ a conventional type of transmitter which may be operated by a slynchronous or non-synchronous motor and/or pon alternating or direct current. A governor vmay beemployed upon the transmitter motor to cause the operation thereof of a substantially prej determined rate. This motor. drives the transmitting scanning members which in turn generate picture currents. At the termination of each transmitting scanning cycle, va synchronizing signal for a particular frequency or amplitude characteristic is generated and transmitted.

At a remotely disposed receiver, the picture and synchronizing signals are detected and are applied to the recording and synchronizing mechanism respectively. The synchronizing pulses if of a by `a friction clutch which is interposed between thedrum and the motor.

' Upon the receipt of a synchronizing signal,v the halting lever will disengage the drum and permit the continued rotation thereof. However, as previously mentioned, since the driving motor is operating at a speed which-is determined by the frequency of the synchronizing pulses the projection on the drum will arrive at the synchronizing lever just as the synchronizing signal causes the removalthereof'. Thus, although the synchronizing lever will operate in response to received synchronizing signals," there will normally be n o start-stop action and the friction clutch engaging the motor and the drum will not operate.

It is only at the beginning of a transmission that. the synchronizing lever operates to adjust the phase position of the scanning member. Also, i

if during the transmission, an interruption should occur which might causea phase displacement,

^ the synchronizing lever will immediately operate distinctivev amplitude lare separated from the received signal and are impressed upon -a thyratron inverter which operates to translate direct curi rent into alternating current at the frequency ofthe incoming synchronizing signals.

This alternating current which is therefore of a frequency that is a function of the speed of the transmitting scanner is applied to a synchronous motor which drives the recording scanner. f

' Again, 'it will be evident that the recording scanner may be caused to operate at a speed identical to that at the transmitter. However, it is necessary in facsimile transmission to ensurethatthe transmitting and recording scanning members operate at the same speed and in the exact phase.

It is obvious that if the recording mechanism is operating at the same rate as the transmitting mechanism, the phasing operation need occur only once during the transmission. or subsequent to any momentaryA interruption which may cause a relative phase displacement. To this. end, I incorporate a. start-stop mechanism into the recorder which mechanism is substantially similar the start-stop mechanism to re-phase the scanning members. f A

It is therefore an object of my invention to provide a facsimile transmitter and recorder which continuously operates in synchronism with each other. v

Another object of my invention is to provide for a`picture transmission system wherein a continuous synchronizing current generated at the transmitter is transmitted with the picture signals. n D 'Still another object of, my invention is to provide for a picture transmission system wherein a thyratron inverter is utilized at the recorder to translate direct current available into alternating current at a frequency which is a function of the speed of the transmitting scanner.

A further 'objectof my invention is to provide for a picture transmission system wherein a series of transmitting synchronizing impulses operate to control a thyratron inverter circuit operable t'o drive a recording motor. l

' It is afurther object of' my invention to provide a facsimile recording system driven by a synchronous motor energized through a direct current source.

Still another object of my invention is to provideA a facsimile recording system which continuouSly operates at the speed and in the same to. thatl which heretofore has been, employedl to maintain synchronism.

In this system, a lever or similar member is in the path of a projection upon the scanning members. The incoming synchronizing signals are impressed upon electromagnetic means which remove the lever from the path of the drum prosimile recorder will operate in the following manner: I

At the beginning of a transmissiomshould the transmitter and' receiver drums be outof phase, the projection on the drum will engagethe synchronizing lever and preclude further rotation thereof. The driving motor is permitted to rotate jection, when energized.' Consequently, this facphase as the transmitter.

Still a further object of my invention is to provide a novel combination of a continuous synchronizing system and a start-stop synchronizing system whereby accurate control over the speed and phase of the recording scanning members is obtained.

These and other objects of my invention will now become apparent from the following-descrip tion taken in connection with the drawings, in which: l

Figure 1 is a schematic illustration ofA a transmitter adapted to transmit a combined picture signal and continuous synchronizing current.

Fisure`2 is another embodiment of a facsimile transmitter operable to generate and transmit combinedpicture signals'and synchronizing impulse s. Figure 3 is a schematic diagram of a facsimile recorder adapted for continuous synchronization with a corresponding transmitter.

Figure 4 is a diagrammatic representation of a facsimile recorder adapted for continuous syn- .-.curreiit lpower supply to the motor. y transmission line 3| causes the modulation'v of fthe. radiolfrequency carrier by an alternating' Vcurrent -of a lfrequency .equal to that -driyingfthc motor I2. Accordingly, the energy radiated from chronization and incorporating a start-stop mechanism for proper phasing thereof.

A facsimile transmitter' for combining a picture current and a continuously synchronizing current is diagrammatically illustrated in Figure 1 and reference is now made thereto. A

transmitting drum I I is rotatably supported and continuously driven by motor I2 through any suitable positive coupling I3. The typeof motor utilized to drive the drum II will be described in a later paragraph.

An optical scanning system I4 is mounted upon a feed screw mechanism and in the well known manner is caused to be displaced axially with respect to the drum II. Thus the light spot I5 traverses a continuous helical path about the surface of the drum. i o.

Light reflected from the drum impinges upon thev cathode I6 of a photoelectric cell I'I winch x is fixed relative to the optical system I4 and thus is displaced accordingly. The photoelectric cell Il energized by battery 2l thus carries a current which varies in accordance withthe lights and shades of the elemental areas of the picture traversed by the light spot l5. This current in passing through resistor 22 develops a 'corresponding voltage thereacross whichis impressed .upon an amplier 23.

The frequencies of the picture currents generated may vary between 0 and a maximum .which is normally an audio frequency. These,

currents are then caused to modulate a relatively low frequency wave in a modulator 24. Thus,

and in accordance rwith a continuously applied alternating current of the driving motor frequency.

If space radiation is employed for transmission as illustrated, then the synchronizing current may be of the same frequency as the motor 'supply current. However, if a telephone'translustrated radio frequency circuits 4l and the associatedantenna 42 are utilized to receive and Vdernodulate the transmitted radio frequency energy. This energy is, as illustrated,- applied to two parallel channels which function'to separate the components of lthe transmitted signal. Thus a. parallel combination or' high pass lter 43 and low pass lter 44 are utilized to selectively transmit the received picture currents and the received synchronizing current respectively.

As schematically indicated in Figure 3, the high pass filter comprisesa combination of series capacitance 45 and shunt inductance 4t.

the output of an audio frequency oscillator 25Y 1 is impressed upon a modulator 24 tube with the amplified picture currents to produce apicture modulated audio frequency. n

current may be amplified to any desired level and transmitted to the remote station. Any transmission `means may of course be ein- 'ployed, namely, a telephone communication line or a radiofrequency transmitter. As illustrated, the picture currents ,are impressed upon a circuit 26 wherein they modulate a radio frequency carrier which is then radiated by means of antenna 21. i

Returning now to the source ofrnotive power I2 which causes rotation of the drum and axial displacement of the optical scanning system, vthe motor I2 is vpreferably a synchronous motor energizedfrom an alternating current supply.'A If an 'alternating current supply is unavailable, then a vibrator and storage battery may be utilized in combination to generate an alternating current oi' approrimately the desired frequency or a. self-excited thyratrcn inverter may 'be em- 'ployed in connection with a. direct current power line to generate alternating currents of the desired frequency. Y

In anyevent, thespeed of the drum II und I the scanner I4 is a function of the frequency of the .impressed'alternating current. To obtain a synchronizing .current which is a func'- tion of the speed ofoperation ofthe combination 'of-drum and optical scanning member, I

therefore connect the radio frequency. carrier.'

Conversely, the low pass lter for discriminatdrum is driven by positive coupling to a Syn- .chronous motor 56 through a gear reduction box 51. Tae gear box 5l also lfunctions to cause suitable rotation of shaft BI which through the agency of vworm 52 and worm gear 63 causes the rotation of feed vscrew 64 as is well known in the Rotation of the feed screw 64 causes axial displacements of a scanning mechanism 65vwhich is through a nutv which engages therewithl The maintained in engagement with the feed screw conductive stylus 5,4 in engagement with a sheet of sensitized recording paper mounted ,upon the conductive drum.

modulatingjcircuit directly to the alternatingV Thus the theantenna 21 comprises ajradio frequency carrlermodulated in accordance with thelights and v shades of the picture supported upon lII y Thus it may be'seen that rotation of motor 56 will cause corresponding rotation of the drum 5l while stylus-54 is displaced axially. The pointl of the stylus thcreforefollows 'a helical pathv whichV -is similar. to that oftheV scanning licht beam at the transmitter' as will hereinafter beexplained. 1 i t -v A The rectified currents maybe impressed upon the rotatable conductor drum I S'in any suitable manner as by a brush and slip-ring andthe like.

The type .of paper employed will de Y termine the level of amplification required for the incomlngpicture signal and a saturable device i is employed.

' negative end a condenser 11 is alternate'ends of former 82 which in turn is energized from the are f alternately secondarye when the nrst tube conducts 4- may be placed in circuit with the stylus to preclude the combustion of the recording sheet. It

will be understood that this invention is not limited to the conductive stylus and platen arrangement illustrated, but may be employed with vany type of transmitting and receiving scanning systems.

-- Thus the amplified picture currents obtained from the rectier 53 could be impressed upon a lamp to vary the intensity thereof and to record upon a photographic or similarly sensitized film.

' The motor 56, as hereinabove mentioned, is of rect current available into this alternating current. The thyratron may be one of several well known forms.

As illustrated in Figure 3, a parallel type, inverter comprising two thyratron tubes 1| and 12 The direct current available for energizing motor 56 is illustrated by battery 13, the of which is joined to the cathcdes of the thyratron tubes 1| and 12 and the positive end vof which is joined to the center tap 14 of the primary of transformer`15 Vthrough reactor 16. The extremities of the primary winding 15 are joined to the anodes of thethyratron tubes, and shunted across grids of the thyratron tubes are energized from the secondary 8| of the transoutput of the low pass filter 44.l

" 4If needed, suitable amplifying equipment may be-placed in circuit with the output of the iilter M to `raise thelevel of; the synchronizing current.

.Thethyratron grids are 'normally biased nega-l tively bythe battery 83. Inoperation, the thyrathe anodes. Thel nating current is induced in the secondary 8l and is in turnimpressed upon the synchronous motor 66. l l

Further it is to be noted that Vthe alternating current developed is of frequency identical with the synchronizing current induced within the transformer 8|. Therefore, the synchronous inotor 56 willrotate at a speed which corresponds to the speed of rotation of the drum Il at the transmitter. The thyratron inverter will translate thedirect current available into alternating current ofthe required frequency and thus continuous synchronization and continuous operation of the recording drum 66 is obtained.

Thus the transmitter and a remotely disposed I receiver will operate in exact continuous synchronism even though the power supply utilized for driving the synchronous motors is not devrivedfrom the same alternating current transmission line.

A further modification of the continuous syn-= chronizing system illustrated 'in Figures l and 3 is illustrated in the transmitter and receiver combination of Figures 2 land 4.v In Figure 2, the transmitter is similar to that which has been conventionally used for the generation of facsimile signals. Thus the motor |0| which is preferably of the non-synchronous type is driven from a power supply which may be either direct or alternating current. This motor is governed to a substantially constant speed by a centrifugal device which operates to open the main circuit when the l speed exceeds a predetermined value.

I trcal cell |05 is caused to move axially troncircuitillustrated translates the power de? livered by battery 13 into alternating lcurrent which is caused to flow in the transformer second ry 84 and which thus energizes the syn-4' ch onousmotor 56.

is wen known, in a gas tron such as 1| or 12, the gridexercis'es control the tube only when there In the circuit illustrated. the grids of the tubes When one grid battery 13 delivers the requiredugrrent. VThis current iiows through the reactor 1l and the secondary(l 16 thus a current nnea mede or thym# Assoon asv conduction is established v.between anode and cathode, the` grid loses control of the space( current and does l not regain'control until conduction ceases.'

driven positive and negativa is driven more 'positive byjthe 'synchronizing current induced within the 0|, its tube conducts and' the amplifiedby the amplier |01 Y audio frequency modulator v n means. ofthe is In the grid ner` H3 frequency modulating and transmission circuits v lll. The output currents are then radiated by antenna |5.- f

The motor l0 I through gear reduction drive |02 positively and continuously drives transmitting drum |03. To this drum is secured the image to be transmitted by any suitable means.

An optical system |04 and associated photoelecwith respect to the drum by means of a feed screw driven from the motor |0| in the manner similar to that schematicallyshown in'Figure 3. vThus a light spot |06 traces a helical path about the drum.

'Ihe variations in light which fall upon the photoelectric cell a/re translated into corresponding iluctuating electric currents which are then and fed tothe ||l with an audio frequency oscillation generated in oscillator H2. Thus the output of the modulator Ill is an ,audio frequency current amplitude modulated in accordance with the lights and shades of picture areas'. This current is then amplified by amplito a suitable level for driving the radio Periodicsuy 'at the termination-of acn revolution of the drum |03, a synchronizing signal-is generated and impressed upon the transmission This synchronizing signal may be generated in a 'manner more `completely described -in my copending application Serial No. 361,480, signal led October 1'7, i940. The synchronizing is generated by utilizing a characteristic indication Ils such as a black stripe across the drum surface. During the period in which this black strip passes under the light beam of the optical scanning system, the switch ||1 is closed by means of cam |2| coupled to the drum by shaft v Closure of switch l|1 as described in the aforementioned copending application raises the amplification level of the circuit. ||3 and thus the 'passage of the Vcharacteristic indication |I6 under nizing pulse at the termination of each scanning lo cycle.

As will become evident from a description of the receiver indicated in Figure 4, various other forms of synchronizing signals may be employed in connection with this type of system. Referring now to the receiver of Figure 4, an antenna |40 is employed to intercept the signals radiated by antenna illustrated in Figure 2. The voltages developed therein are demodulated in the radio frequency circuits |4| and impressed upon an amplifier |42. The output of the amplier |42'wil1 comprise the combination of synchronizing impulses and picture currents.

' As illustrated, one circuit from the output of .amplifier |42 is fed to a full wave rectifier |43,

the output of which is impressed between the conductive rotatable drum |44and a conductive recording stylus |45. Attached to the drum |44 by means of shaft |46 is a cam |41 having a projection |5| which operates once during each drum revolution to 'interrupt the circuit through cam switch |52.

Interruption of this circuit, asV

pulses are rich in harmonics and thus a high harmonic thereof may be employed. These pulses are impressed between the grid and cath` ode-of a thyratron tube |51, the grid of which is biased to a suitable valueby means of battery |6|. The inverter illustrated is known as a relaxation type in that a single gas filled triode is employed.

As illustrated, the vpositive terminal of the main direct current supply |54 is joined at the ganode of the thyratron |51 through inductance |62 and the primary |63 of an output transformer |64. A series circuit of a condenser |55 and inductance |66 shunts the anode to the cathode of the gas filled tube. When the grid of the thyratron |51 is driven more positive'with respect to the cathode by an incoming synchronizing pulse or bythe positive cycle of ka higher harmonic thereof, the tube will conduct and a surge of current will iiow in the primary |63 of transformer |64 and so induce a corresponding current in the secondary |61.

The circuit of condenser |65 and |66 acts as a commutator and causes the extinction of the y thyratron |51 subsequent tothe discharge therewill be obvious, precludes current flow between the conductive stylus andthe drum |44.

is arranged with respect to the drum and with 'respect to the incoming signals so that the currents are interrupted cyclically during the reception of the synchronizing signal.

This of course prohibits the recording of the high level synchronizing pulse which may aii'ect the recording sheet.-

Another parallel circuit from the output of amplier |42 is joined to a synchronizing pulse am- AS will hereinafter be explained, the projection |5| such a circuit is biased to preclude the iiow of normal picture currents and thus the output of the synchronizing pulse amplifiers. |53 isv merely a succession of synchronizing signals.

It is to beremembered, that any form of syn vchronizing signal may be employed. Thus if synchronizing signals of a distinctive frequency characteristic were transmitted. a selective filter y would be used at thev receiver to separate these from the picture currents and transmit them through the synchronizing pulse channel indicated.

The synchronizing pulses appearing in the output of-ampliiier |53 are used to synchronize a thyratron inverter operating to translate a direct current power supply l| 54 at the receiver into alternating currents of a frequency suitable for driving the synchronous motor |55. If the frequency of the incoming synchronizing pulses is relatively low as compared with the frequency of the desired alternating current, a frequency multiplier |56 may be utilized to raise the frequency to that desired. Obviously it would be easy to raise the frequency since the succession of` synchronizing As described above, it is not only necessary that the recording drum be in rotational synchronism with the transmittingV drum but in exact phase synchronism therewith. The reason for this becomes apparent if it is recognized that an overlapping exists at the transmitting image and :at the recording sheet which is mounted upon the drum |44.

Thus it is extremely important that the stylus |45 begin to record the picture immediately following the overlap period on the recording drum |44 and terminate the recording of this picture just prior to the passage of the paper overlap under the recording stylus. At the transmitter illustrated in Figure 2 it may be seen that the 'position of the characteristic indication ||6 and the position of the projection on the cam |2| determine the position of the synchronizing impulse with respect to the overlapof the image to be transmitted. In fact, as indicated in the copending applicationl above mentioned, the image mounting means is colored black in order that the synchronizing pulse be generated exactly during the overlap period. Consequently, to ensure proper phasing at the receiving circuit even though I employ a continuously synchronized drum as regards speed of rotation, I utilize a novel combination of continuous synchronizingv and a start-stop mechanism.

As illustrated schematically in Figure 4, the synchronous motor |55 drives the drumv |44 through a friction clutch |1| which comprises a driving plate |12 coupled directly to the motor shaft |13, a driven plate |14, coupled directly to the drum |44 through shaft |15 and an interposed layer of leather or similar frictional backing |16.

Al spring may be used to maintain frictional engagement between the three elements |72, |14 and |76 of the clutch. A synchronizing lever |11 pivotally mounted by a chain |8| is normally biased by means of tension spring |82 so that the edge Ill' is in the path of a p-rojection |14' on the driven plate |74.

will engage the lever |11 to permit slipping within the clutch and to halt the rotation of drum |44.

However. as indicated in Figure 4, the output of the synchronizing pulse amplier also energizes a synchronizing electromagnet |83. This magnet when energized will attract the magnetic member |84 and cause the rotation of synchronizing lever |11 about the pivot |8|. This will remove the end |11' from the path of the projection |14' to permit unimpeded rotation of the drum.

If at the beginning of a transmission, the overlap of the drum |44 is out of phase with respect to the overlap of the drum |43, the synchronizing lever |11 will preclude rotation of the drum |44 until a synchronizing signal is received to energize magnet |83. At this point the drum I 44 will be released to rotate under the driving iniluence of motor |55.

However, as previously mentioned, the driving motor is operated through thyratron inverter |51 which is in turn energized by a synchronous alternating current. Thus rotation of drum |44 will occur at exactly the same speed as the transmitting drum |03. Therefore, the projection |14' on the driven plate |14 will arrive at the edge |11' of the synchronizing lever just as the synchronizing signal arrives and draws the lever out of the path of the driven plate.

Due to this action, the friction clutch will not operate during the normal picture recording cycle but will only operate if the recording drum |44 falls out of phase with respect to the transmitting drum |03. This condition may prevail at the beginning of a picture transmission where it is diicult to ascertain the exact position of the recording drum; also if any line or transmission faults occur which tend to interrupt the signal and thus tend to slow down motor |55.

Under these circumstances, the friction clutch will operate to maintain. proper phasing of the transmitting drum. Although it is possible to operate the drum in a start-stop phase, this will rarely occur since it is seldom that line faults will cause misphasing thereof. Therefore, the above described modication of facsimile transmitter and recorder taken in connection with Figures 2 and 4 provides a system in which continuous synchronization is obtained by the use oi a thyratron tube which translates direct current into alternating current power for consumption by a synchronous motor, at the synchronous desired frequency.

Furthermore, this system compensates for any misphasing condition which may arise at the beginning of a transmission or in the course of a transmission. It will be evident that any form `of synchronizing signal may be utilized for the type of circuit indicated in Figure 4.

If the constant frequency continuous type of synchronizing signal is employed, then it will be necessary to combine `this with the transmission ol impulses at the end of each scanning line for the operation of the synchronizing magnet. By an amplitude discriminating means, these amplitude synchronizing pulses may bel separated Accordingly, during the vrevolution of the drum |64, the projection |14' TJI ger/avea from the continuous synchronizing signal and be applied to the electromagnet |83.

Thus it is evident that a combination of the transmitters illustrated in Figures 1 and 2 ard the recorders illustrated in Figures 3 and 4 is possible and that any form of synchronizing signal may be employed. Either system eliminates the constant wear which has normally been experienced by prior start s'top systems, The drums are continuously rotated and if they are stopped at all, it is for repliasing, which is a necessary feature.

It should be noted that the thyratron circuits employed are driven from a direct current source which is capable of delivering enough power to drive facsimile signalling motors. [power rat-ing of this type motor is of the order of thirty to sixty watts and as is well known, such power is easily handled by gas filled triodes or thyratrons.

Since the specic disclosure hereinabove set forth relating to continuous synchronizing systems and combined start-stop and continuous synchronizing systems may be subject to continuous modification by those skilled in the art and still fall within the spirit and scope of my invention, I prefer to be bound only by the scope of the appended claims.

I claim:

1. In a signalling system, a transmitter and a receiver, movable members at said receiver and said transmitter, means for motivating said movable members at said transmitter, and means for transmitting a signal which is a function of the speed of said transmitter movable members, a direct current source of power at said receiver,

* means for receiving said transmitted signals and means including an electronic circuit, said redirect current source of power at said receiver,

means for receiving said transmitted signals and means including an electronic circuit, said received signal and said source of power for motivating said receiver movable members at the speed of said transmitter movable members, said electronic circuit comprising a gaseous discharge tube inverter for translating said direct current power into alternating current, said inverter operating in accordance with said received signal.

3. In a picture transmission system, a transmitter and a receiver, a scanning member at said i transmitter for translating the lights and shades `of an image into correspondingly fluctuating image currents, means for motivating said scanning members, and means for generating a synchronizing current having a, frequency which is a function of the speed of :aid scanning members, .means for transmitting said image currents andsaid synchronizing currents, a source of power at said receiver, means for receiving said transmitted currents, a scanning member at said receiver for converting said received image currents into an image, means for motivating said Normally the nizing receiver scanning member including said power source, said received synchronizing currents and an electronic'circuit. 4. In a. picture transmission system, a trans-` mitter and a receiver, a scanning member at said transmitter for-translating the lights and shades of an image into correspondingly uctuating image ourrentsfmeans for continuously motivating said scanning members, and means for generating a synchronizing current having avfrequency which is a function of the speed of said scanning memf bers, means for transmitting said image currents.

and said synchronizing currents', a direct current source of power at said receiver, means for receiving said transmitted currents, a scanning member at said receiver for converting said received image currents into an image, means for motivating said lreceiyerscanning member including said power source, said received synchronizing currents andan electronic circuit operable to translate said direct current power into ternating current power at a frequency which a function o f the frequency of said synchro- 5. In ter and a receiver, a scanning member yat said a picture transmission systemfa transmitagecurrents, a synchronous motor foi-'continuously motivating said'scan'ning member, a source of alternating current for energizing said synchronoussmoto'r, means for transmitting said image currents and an-uninterrupted synchronizing current of frequency equal to-said alternating current, means at `said receiver for receiving said .transmitted currents, a source of power at said receiver, scanning membersat said receiver for recording said image currents, means'for-motivating said 'receiver scanning members at the speed of said transmitting scanning membersincluding a synchronous motor, said'receiver power source, said received synchronizing current and athyratron tube having a control grid and anode,

said thyratron being 'operative totranslate the power of said receiver power source into alternating current, said received synchronizing cur- .rent being selectively impressed upon said control grid for determining the frequency of said alter- .nating current,said alternating current energizing said synchronous motor.

8. A picture receiver comprising means for receiving transmitted image currents andr uninterrupted' synchronizing currents, scanning members forrecording said image currents, means transmitter for translating the lights andy shades of an image into correspondingly fluctuating image currents, means for continuously motivating said scanning members, and means for generating a synchronizing current having a frequency which is -a function ofthe speed of said scanning members, means for transmitting said image currents and said synchronizing currents, a-scurce of power at said receiver, means for receiving said' transmitted currents, a scanningmember at said lreceiver for converting said received image currentsinto an image, means for motivatingsaid i receiver scanning member at the speed of said transmitting scanning member, including a synchronous motor, said power source, said receivedsynchronizing currents and an electronic circuit operable to translate -said direct current power into alternating current. power of a .frequency which is a function of the frequency of said synchronizing current for energizing said synchronous motor.

6. In a picture transmission system, a transmitter and a receiver, a scanningmember at said transmitter for translating the lights and shades of an image into correspondingly fluctuating image currents, a synchronous motor for continu ouslymotivating said scanning '.mexnber, a source of alternating' current for energizing said -syn-A chronous motor, means for transmitting .said limage currents and an. uninterruptedv synchronizing current of f requencyequa-l to'saidV altervnating current, means .atsaid receiyer for receiving said transmitted currentsfa source of 'power at said receiver,` scanning members at said receiver for recording said image currents, means for motivating' said receiver lscanning members at the speed ofsaidtransmitting scanning\mem bers includinga synchronous motor, .said receiver power source, saidV receivedfsynchronizing cur rent and a thyratron tube having a central grid' and'anoda said thyratron being operative to i rents upon said scanning members.

- 9. -A picture receiver comprising means for receiving'transmitted image currents' and uninterrupted synchronizing currents, a rotatable drum for carrying a recording sheetgand, a recording scanner for traversing said sheet, a synchronous motor positivelycoupled to said drum and to saidl scanner, a direct current power source, means for translating said direct current power int'o alterhaving a control grid, an anode and an anode circuit, said synchronous motor-being coupled to said anode circuit, said direct current source translate the power ofsaid receiver power source f into alternating currents at said synchronizing current frequency for energizing said synchronousl motor.

7. In a picture transmission systemfa transmitter and a receiver, a scanning member at said for translating the lights kand shades of an image into correspondingly fluctuating imbeing in said anode circuit, said synchronizing i currents being impressed -upon saidgrd.

10. A 'picture receiverl comprising means. for

g nating current powercomprisi'ng a thyratron tube receiving transmitted image currents and uninterrupted synchronizing currents, a rotatable drum for carrying a recording sheet-7 and a re'- cording scanner` for traversing said sheet, a synchronous motor positively coupled to said drum f and to said. scanner',v a direct c'urrent power source, means for translating said direct current power into'alternating current power comprising a thyratron tube havingv a control grid, an anode. and an anode circuit, said synchronousV motor being coupled to said anode circuit, Vsaidjdiiect current source being in said` anode circuit, said synchronizing currents being selectively impressed upon'said grid andsaid image currents being vselectively impressed upon said. scanner.

11. In a picture transmission system, a transmitter comprising a rotatable drum for supporting an image, a synchronous motor for driving V member cooperable with said drumfor translating the lights and shades of said image'intoeon" v said drum, an alternating' current supply for en-4 ergizing said synchronous-motor, a scanning,

respondingly varying image'currents, means for generating a phasingv signal at the termination by and disposed. second station ber; a source of driving power for said first stasaid drum, an alternating current supplyfor energizing said synchronous motor, a scanning y member cooperable with said drum for translating the-lights and shades of said image into cor- Y respondingly varying image currents, means for Y signals to be transmitted;

generating a phasing impulse of distinctive ampliy .tude at the termination of each drum revolution, and means for transmitting said image currents, said phasing impulse and a current of the frequency of said alternating current.

13. In a signalling-system; a rst station having a movable member; a remotely disposed sec- A ond station having a movable member; a source of driving, power for said rst station, and a source of driving power for said second station; means at said first station for generating picture signals to be transmitted; means at said second station for receiving said signals; a source of electrical energy at said second station for operating its associated source of driving power: means at said first station for generating synchronizingsignals which are directly controlled are a function of the speed of operation of said rst station movable member and means at said second station for source of electrical energy, signals of a. frequency which is a function of said synchronizing signals for determining the speed of operation of said receiver.

' 14. In a picture transmission system; station having a movable member;

a ilrst a remotely having a movable memtion, and a source of driving power for said second station; Aeansat said first station for generating picture signals in accordance with. the

lights and shades of a picture to be transmitted; meansl at-said second station for receiving said picture signals and translating them back into lights and shades for recording; a source of electrical energy at said second station for operating its associated source of driving power; means at said rst station for generating synchronizing signals which Vare directly controlled by and are .a function ofthe speed of operation of said first station-movable member, and a thyratron inverter at said second station for producing from said source of electrical energy, signals of a frequency which is afunction of said synchroniiting signals for-determining the speed of operation of said receiver.

l5. In a signalling system; a rst station having a movable member; a remotely disposed second station having a movable member; ga source of driving power for said first station, and.v a

producing from said.

source of electrical energy,

source of `driving power for said second station; means at said first station for generating picture means at said second station for receiving said signals; a`source of electrical energy at saidv second station for operating its associated source of driving power; means at said first station for generating synchronizing signals which are directly controlled by and are a function of the speed of operation of said first station movable member, and means at said second station for producing from said signals of a frequency which is a function of said synchronizing signals for determining the speed of operation of said receiver; means for periodically transmitting a phasing signal controlled by the position of said first station movable member, and means at said second station responsive to said phasing signal only when said movable member thereat is out of phase with said first station movable member for bringing-them into phase.

16. In a signalling system; a rst station having a movable member; a remotely disposed second station-having a movable member; a source source of driving power for said second station;

vmeans at said rst station for generating picture signals to be transmitted; means at said second station for receiving said signals; a source of electrical energy at said second station for operating its associated source of driving power; means at said rst station for generating synchronizing signals which are directly controlled by andare a function of the speed of operation -of said first station movable member for transmitting a harmonic of said ysynchronizing signals; and means at said second station for producing from said source of electrical energy, signals of a frequency which is a function of said synchronizing signals for determining the speed of operation of said receiver.

i7. In a signalling system; a first station having a movable member; a remotely disposed second station having a movable member; a source of driving power for said first station, and source of driving power for said second station; means at said first station for generating picture signals to be transmitted; means at said second station for receiving said signals; a source of electrical energy at said second station for operating its associated source of driving power; means at said first station for generating synchronizing signals which are directly controlled by and are a function of the speed of operation of said first station 

